1. Field of the Invention
The present invention relates generally to agricultural implements with adjustable wheel spacing and, more specifically, to a self-propelled chemical applicator having hydraulically adjustable rear wheel spacing for accommodating different row widths and patterns.
2. Related Art
Presently available self-propelled sprayers such as the John Deere Model 6000 Hi-Cycle Sprayer have a frame supported a substantial distance above the ground on a forward steerable wheel and on drive wheels supported by a pair of rear drop assemblies. The drop assemblies are attached to a transverse rear cross axle tube and are adjustable so that the tires run between rows of plants. The wheel tread therefore depends upon the row spacing and must accommodate many different row spacings and patterns including skip row patterns. Adjusting row spacing on the current 6000 Hi-Cycle Sprayer is relatively time-consuming and requires lifting of the wheel, removing eight bolts and nuts, prying the drop axle to the desired location on the cross tube so that bolt holes align, and thereafter installing and tightening the eight bolts and nuts.
Power-operated devices such as a threaded drive shaft shown in U.S. Pat. No. 4,350,222 have been proposed to decrease the time and effort required to adjust wheel tread on a sprayer. However, such threaded drive devices are subject to binding in the harsh environmental conditions encountered by an agricultural sprayer. In addition, most previously available devices including those on the 6000 Hi-Cycle and on the device shown in the aforementioned U.S. patent include slide structures which connect the drop assembly to the rear cross axle tube or rail structure and present friction and freezing problems, particularly since rusting is a very common problem on chemical applicators.
Any movement between the drop assembly and the cross axle tube during field operations can result in plant damage as a wheel runs too closely to or directly on a row of plants. Therefore, the clamping arrangement must effectively secure the drop assembly against transverse movement.